A first line of defense considered for most neurological disorders is treatment with psychoactive medicines, prior to any surgical intervention. Psychoactive medicines or drugs are those capable of acting on the nervous system and affecting mental states and behavior. Many physiological mechanisms are aided by such drugs, but these medicines have unwanted side effects, drug interactions, and long-term physiological tolerances that render the drug less effective over time.
In the case of Parkinson's disease that serves as the exemplar disorder herein, the underlying etiology is that neurons, located in the substantia nigra of the mid-brain, for some unknown reason begin to produce less dopamine. As these neurons progressively and relentlessly deteriorate over years, less dopamine dramatically affects the motor control of the basal ganglia and thus outward behavior and everyday living. An estimated 1.5 million Parkinson's patients have a visible cluster of diagnostically significant and debilitating Parkinson's symptoms, typically tremors, stiffness, slowness, and balance. Patients describe the internal feeling as frozen still in the “set” stage of the “ready, set, go” sequence that started of a race.
The “gold” standard treatment for Parkinson's is frequent daily administration of an indirect dopamine replacement, L-Dopa, a psychoactive drug that crosses the blood-brain barrier, and then alters form to produce dopamine as a supplement to the brain's own production. This therapy, while initially quite beneficial, typically can lose much of its effectiveness over about five years, wherein patients have to take progressively larger and more frequent doses until eventually the result becomes inadequate. Without alternative drug therapies, patients are left to suffer both the ravages of primary symptoms and the manifestations resulting from the prolonged use of the drug itself, principally the repetitive spasmodic motions of dyskinesia. More than one million people endure these symptoms, including such notables as the Pope, Muhammad Ali, and Billy Graham, while thousands of others including Michael J. Fox have turned to surgical approaches.
Past surgical techniques treated symptoms of these diseases by selectively and permanently destroying or ablating structural areas in the brain. The net effect is to “shut the door”, in a neurological fashion, before dysfunctional brain signals are sent to the muscles, thereby relieving many symptoms. The advantage of surgical ablation is that it reduces the reliance on drug therapy with its attendant side effects. The disadvantage is that the procedure is irreversible. This may render such patients as unacceptable candidates for newly discovered techniques/therapies, such as stern cell implantation or viral transport of genome-altered DNA (deoxyribonucleic acid), both of which show promise in helping to augment or even to regenerate the natural production of dopamine as well as a number of other substances involved in neurological disorders.
Certain neurological disorders that produce debilitating motor symptoms are now being treated with Deep Brain Stimulation (DBS) through-skull implanted electrodes see FIG. 1 below. DBS essentially reversibly alters the local neurological structure(s) around the tip of an electrode implanted on the brain with electrical pulses that reduce or stop disabling symptoms, such as, but not limited to, severe tremor and rigidity found in Parkinson's disease.
DBS functionally has the advantage of emulating ablation by changing the firing characteristics of nearby neurons, but it does so only while the pulsed stimulation persists. Since the structures remain intact and undamaged, when DBS is turned “off” these structures reactivate and symptoms return, unless otherwise treated. Thus, DBS overcomes the chief disadvantage of ablation in that it allows implanted simulators to be withdrawn later for new techniques, with minimal residual effects. In 1998, the Federal Drug Administration (FDA) approved DBS as an alternative for, or as an adjunct to powerful psychoactive drugs (neuro-medicines) burdened with strong and often unacceptable side effects.
The only FDA approved DBS apparatus is currently being sold by Medtronic, Inc., 710 Medtronic Parkway, Minneapolis, Minn. 55432-560, see FIGS. 2 and 3 below, although other companies have substantial interests in implantable neuro-stimulation devices for a variety of neurological disorders, such as Advanced Bionics, Corp., 12740 San Fernando Road, Sylmar, Calif. 91342; see “http://www.advanced bionics.com.” However, there are problems with the approved apparatus.
At the very least, the presently approved apparatus is cumbersome and uncomfortable for many in its present form. As an outgrowth of legacy components from heart “pacemakers,” it consists of one or two remote stimulator/battery packs embedded under muscle tissue in the upper chest area, and requires subcutaneous leads up along the neck to the skull entry point. All these components are subject to corrosion and breakage, as well as to resistance or attacks by the body itself attempting by encapsulate it or dissolve it, leading to infection.
Medtronic currently uses a product called a Soletra™ Neurostimulator (see FIG. 4 below) to generate a continuous series of electrical pulses, typically at about 2-4 volts, to electrode(s) implanted in specific brain areas. Neurons, normally operating in the tens of milli-volts range, are massively over-stimulated by such voltage and temporally altered, thereby inhibiting the expression of certain motor dysfunctions. Pulse voltage is usually adjusted somewhat depending on the proximity of the electrode(s) to the targeted area, e.g., more voltage is needed for target variations. Typical pulse rates range around 130-185 pulses/second.
This combination of large amounts of voltage, amperage, and duty cycle creates a power drain that normally requires a non-renewable battery replacement in about 3-5 years, at a price of about $10,000. Many patients turn “off” the stimulation when going to sleep while tremor is quelled, in order to conserve power. Current DBS stimulator(s) are designed to be turned “off” or “on” using a magnetic-switch placed briefly near the associated electronics.
Thus, without considering the remote apparatus itself, or the power requirements of the present design, a goal in this field should be to reduce stimulation-related side effects and complications caused by stimulating in the vicinity of the target. Two key objectives to meeting that goal are for the surgical implant to hit the center of a targeted cellular region, often not more than 2 mm across in any direction, and for the current field to stimulate the appropriate cells for symptom reduction or cessation, without triggering side effects in adjacent structures.
While the surgical techniques themselves are well documented, the surgery is still a unique combination of art and science [see Lozano, Andres M. (Ed): Movement Disorder Surgery: Progress in Neurological Surgery, vol. 15, pp. 202-208, Basel, Switzerland: Karger A G, 2000, ISBN 3-8055-6990-4].
A key to a successful outcome is the precise positioning and placement of the electrode(s), aided pre-operatively by vast improvements in brain imaging techniques, but nevertheless requiring considerable surgical skill and judgment. Beside normal variations in brain structures themselves adding to the difficulty of targeting, during surgery the brain moves with each heartbeat, while its size, and position vary somewhat as a result of the surgical probe itself altering internal pressure. During the procedure, the use of fluoroscope imaging assists y-z axis positioning, and awakening of the patient while in the operating room for testing of clinical signs can reveal and help avoid untoward side effects. However, but the final outcome can only be assessed post-operatively. Results can vary by patient and over time. Some post-surgical adjustment is normally done with electrical parameters and z-axis programming of one or more of the electrode contacts available on the current DBS electrode, as is described below, but not to the extent that many physicians would like and not with respect to the x-y axis.
Current DBS electrodes have four (4) circumferential contacts that radiate current in a 360 degree configuration. This means that with any degree off-target, or unnecessary stimulation even on target adjacent cells are exposed to current and potential side effects. While some of these side effects may be adjustable when electrical parameters are altered, or even reversible when the stimulation is shut down, but the cost is decreased efficacy of stimulation on the symptoms. For example, in sub-thalamic nucleus DBS, stimulation-induced side effects may include increased dyskinesias, blepharospasm or so called “eyelid-opening apraxia,” confusion/memory disturbances, personality changes, mood changes, apathy, cognitive changes, dysphonia/dysarthria, and such.
Medtronic Inc. has proposed a “Directional Brain Stimulation and Recording Leads, title, in U.S. Published Patent Application 2002/0183817 to Van Venrooij et al., which is incorporated by reference. The proposed technique uses a “controller” as shown and referenced to FIG. 32 for recording “brain activity signals” to activate electrodes. However, this technique requires continuously generating pulsed type signals once the electrodes are activated whether or not a brain type tremor has ended, which would result in needless, unwanted and potentially-excessive electrical current being continuously generated inside the brain. The more unnecessary pulse type signals, the more undesirable side effects to the patient, for example, in thalamic DBS, stimulation-induced side effects may include paresthesias, muscular cramps, dystonia, dizziness, dysarthria, gait and balance disturbances, limb ataxia, impaired proprioception, and decreased fine motor movements.
Additionally, this technique would require excessive power to operate, which is not only expensive since battery power supplies would need to be regularly replaced but also require large card-deck size batteries that must be mounted inside of the patient's upper chest area. This proposed Medtronic technique would also be prone to circuit problems since the electrodes would be simultaneously operating as both transmitters and sensors, causing excessive and unnecessary power drain, shortening the lifespan of any batteries being used as well as increasing the costs for replacing the batteries.
According to the Movement Disorder Society© 2002, “Deep brain stimulation for the alleviation of movement disorders and pain is now an established therapy. However, very little has been published on the topic of hardware failure in the treatment of such conditions irrespective of clinical outcome. Such device-related problems lead to significant patient morbidity and increased cost of therapy in the form of prolonged antibiotics, in-patient hospitalization, repeat surgery, and device replacement [Joint, C., Nandi, D., Parkin, S., Gregory, R., and Aziz, T. Hardware-Related Problems of Deep Brain Stimulation. Movement Disorders, Vol. 17, Suppl. 3, 2002, pp. S175-S180.]
Thus, the need exists for solutions to the problems encountered in the prior art.